... 1.diameter:16-25mm 2.used for in mines,tunnel 3.ISO,SGS,BV.professional factory 4.low ... .Diameter:16mm,18mm,20mm,22mm,25mm2.used for in mines,tunnel3.ISO,SGS,BV4. low price, good quality5. ... rolled thread. this bolt has been approved in Gold Mines of Elorado China.1,Features:1. Grooved bolt ... larger diameter borholes.2. Used for permanent support in mines and tunnels.3.with pin nut device, nut could ...